Daughter's Inspiration Creates Unique Thermochromatic Films

You’ve heard of mood rings. They supposedly change color as your mood changes. In fact, they are made of crystals that change as temperatures change -either yours or the ambient atmosphere. It’s a clever idea that goes back to the 1970s. A fast-food ice cream chain had spoons that changed colors. Hyper color T-shirts shifted color with heat. Now comes an announcement from well-known compounder, RTP, of a plan to help develop a new line of thermochromic/thermochromatic materials patented for use in waterproof, flexible applications such as raincoats. ”Our patented, one-of-a-kind ChroMyx product line visually indicates temperature differences through color change,” says Debra Aperfine, president of a new company called Chameleon, based in Oak Ridge, NC. “These color-changing properties will enhance old products and inspire the imagination for new products in multiple industries,” adds Aperfine, who is a co-inventor of the waterproof application.

A thermochromatic dye compounded into a resin system appears transparent until the material reaches a certain temperature. Then due to an electron exchange, the color pigment of the dye is released from encapsulation and the material takes on the color of the pigment. Thermochromic materials can be formulated to change color based on specific temperatures.

Compounds incorporating ChroMyx can even operate above 200F, depending on the resin and dye system used. In an example provided in a patent, a raincoat that is pink at room temperature changes to purple when the temperature of the PVC material drops below 62F. The thermochromatic dyes described in the patent are conventional dyes. The encapsulation system and how the dye is released, are critical to Chameleon’s technology, Aperfine, said.

A unit of RTP called Wiman has been working with Chameleon to test the economic feasibility of ChroMyx. Wiman uses a cast extrusion process that can laminate a cloth or fiber backing during extrusion. “These materials can be laminated, RF-sealed, stitched, and even printed on,” says Aperfine. “ChroMyx can be used in any current or new products needing a vinyl, synthetic leather, or flexible film, or even in woven textiles.”

There are some issues with the material:

1) It can be pricey. A raincoat made with Chromyx costs $75-plus. The cost isn’t due strictly to the dye. Even the resin systems are different. For example, Chameleon only uses vinyls that are RoHS compliant, phthalate free and contain no DEHP plasticizers.

2) Thermochromic dyes, including ChroMyx, are not suitable for extended sunlight/UV exposure. “We are trying to find a system that works,” says Aperfine, “because it would open up so many applications.”

What may be most interesting about this product is how it was developed: “My seven-year-old daughter had a dream that her raincoat was changing colors,” says Aperfine. “She was wearing her purple raincoat and she was playing in the rain. It changed to hot pink. She shared that. As a mother I wanted to get her this fabric. I started looking and couldn’t find it. I was familiar with the hypercolor T shirts, but they aren’t waterproof.” She received help from institutions in Maine, and started working with polymer and dye experts. “I was just very determined that someone somewhere would make her raincoat. I was told along the way by experts that there were multiple reasons why this could never be done. It had to do with particle size of the thermochromatics.” The partners, such as Wiman were also determined to solve the problem. “I am not a chemist.,” Aperfine says. ”I was very blessed to have many experts take me under their wings.”

Her company launched 18 months ago. For information, call 336-643-0157.

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